The ''Coriobacteriia'' are a class of

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. The Gram stain is ...

bacteria within the

Actinomycetota The Actinomycetota (or Actinobacteria) are a diverse phylum of Gram-positive bacteria with high GC content. They can be terrestrial or aquatic. They are of great importance to land flora because of their contributions to soil systems. In soil t ...

phylum.Ludwig, W., Euzéby, J., Schumann, P., Busse, H. J., Trujillo, M. E.,Kämpfer, P. & Whitman, W. B. (2012). Road map of the phylum Actinobacteria. In: Bergey's Manual of Systematic Bacteriology, pp. 1–28. Eds. M. Goodfellow, P. Ka¨mpfer, H. J. Busse, M. E. Trujillo, K. Suzuki, W. Ludwig & W. B. Whitman. Springer-:New YorkClavel T, Lepage P & Charrier C. (2014). The family Coriobacteriaceae. In: The Prokaryotes, pp. 201-238. Springer-:Berlin Heidelberg Species within this group are nonsporulating, strict or facultative

anaerobes An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenat ...

that are capable of thriving in a diverse set of

ecological niches In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for e ...

. '' Gordonibacter'' species are the only members capable of motility by means of

flagella A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

within the class. Several species within the ''Coriobacteriia'' class have been implicated with human diseases that range in severity. '' Atopobium'', '' Olsenella'', and '' Cryptobacterium'' species have responsible for human oral infections including

periodontitis Periodontal disease, also known as gum disease, is a set of inflammatory conditions affecting the tissues surrounding the teeth. In its early stage, called gingivitis, the gums become swollen and red and may bleed. It is considered the main c ...

halitosis Bad breath, also known as halitosis, is a symptom in which a noticeably unpleasant breath odour is present. It can result in anxiety among those affected. It is also associated with depression and symptoms of obsessive compulsive disorder. Th ...

, and other endodontic infections. '' Eggerthella'' species have been associated with severe blood bacteraemia and

ulcerative colitis Ulcerative colitis (UC) is one of the two types of inflammatory bowel disease (IBD), with the other type being Crohn's disease. It is a long-term condition that results in inflammation and ulcers of the colon and rectum. The primary sympto ...

Molecular signatures and phylogenetic position

Historically, all ''Coriobacteriia'' species were placed within a single order (''Coriobacteriales'') and a single family (''Coriobacteriaceae''). This view, however, was not reflective of accurate evolutionary interrelationships within the class. The current taxonomic view is justified by the presence of several

conserved signature indels Conserved signature inserts and deletions (CSIs) in protein sequences provide an important category of molecular markers for understanding phylogenetic relationships. CSIs, brought about by rare genetic changes, provide useful phylogenetic markers ...

(CSIs) that have been found at the different taxonomic ranks. These CSIs are specific and represent

synapomorphic In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

characteristics that can be used to distinguish groups within the ''Coriobacteriia'', both at the family and order levels. The distinction of the orders within the ''Coriobacteriia'' is also supported phylogenetic tree branching and by consistent characteristics; members belonging to the ''Coriobacteriales'' are glucose-fermenting, saccharolytic species while the ''Eggerthellales'' order has species that are consistently unable to ferment glucose and are asaccharolytic. CSIs have also been used to resolve the phylogenetic position of the ''Coriobacteriia'' among all bacteria where they have been found exclusively for all species within the class, delineating them from other

. The ''Coriobacteriia'' are an early branching lineage within the Actinomycetota phylum The deep branching of the class has led to dispute over its membership within the phylum and whether or not it is a true Actinomycetota group. A CSI in the form of a single amino acid insert in the enzyme deoxyuridine 59-triphosphate (dUTP) nucleotidohydrolase has been found that is shared by all ''Coriobacteriia'' members, as well as several Actinomycetota species, and absent from all other bacteria. This CSI provides unambiguous support for ''Coriobacteriias membership within the Actinomycetota.

Phylogeny

The currently accepted taxonomy is based on the

List of Prokaryotic names with Standing in Nomenclature List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the naming and taxonomy of prokaryotes, following the taxonomy requirements and rulings of the International Code of Nomenclatu ...

(LPSN) and

National Center for Biotechnology Information The National Center for Biotechnology Information (NCBI) is part of the National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The NCBI is lo ...

(NCBI).

References

{{Taxonbar, from=Q26211126 Gram-positive bacteria Bacteria classes